Most manufactures uses letters for the model series, but also for the carriage size. So a Komatsu pc220 LC, means a long carriage. A Cat 330BL, the "B" is model series is the these can last anywhere from 3 years to 14 years depending on how much changes are made to the machine. The "L" stands for the long carriage.

For Example a Cat 330CL will be different than a Cat 330BL. Due to some changes made to the model.

Hope that helps.